n-VO2/p-GaN based nitride–oxide heterostructure with various thickness of VO2 layer grown by MBE

Abstract High quality VO 2 films with precisely controlled thickness were grown on p-GaN/sapphire substrates by oxide molecular beam epitaxy (O-MBE). Results indicated that a distinct reversible semiconductor-to-metal (SMT) phase transition was observed for all the samples in the temperature dependent electrical resistance measurement, and the influence of VO 2 layer thickness on the SMT properties of the as-grown n-VO 2 /p-GaN based nitride-oxide heterostructure was investigated. Meanwhile, the clear rectifying transport characteristics originated from the n-VO 2 /p-GaN interface were demonstrated before and after SMT of the VO 2 over layer, which were attributed to the p - n junction behavior and Schottky contact character, respectively. Moreover, the X-ray photoelectron spectroscopy (XPS) analyses confirmed the valence state of vanadium (V) in VO 2 films was principally composed of V 4+ with trace amount of V 5+ . The design and modulation of the n-VO 2 /p-GaN based heterostructure devices will benefit significantly from these achievements.